The present invention relates to a working enclosure of the type including a working chamber whose walls delimit a confinement space for working in and an external branch loop for recycling the atmosphere of the confinement space and which opens into the confinement space at both ends and includes means for circulating the atmosphere in the branch loop.
Conventional working enclosures of the above kind are routinely thermostatically controlled so that the confinement space is maintained at constant temperature and auxiliary systems are routinely used to procure a high relative humidity.
Enclosures of the above kind are used for working in a controlled atmosphere, for example. One example of such work is the culture of animal cells or embryos. In this case the CO2 and water vapour content of the atmosphere in the confinement space in particular are monitored.
Depending on the use to which the enclosure is put, it can be contaminated by undesirable germs which develop in the confinement space.
Recycling the atmosphere of the enclosure via an external branch loop provided for this purpose enables continuous treatment, and in particular filtering, of the atmosphere of the enclosure.
A fan or a pump is mounted in the branch to circulate the atmosphere.
A filter is provided at the entry end of the pipe constituting the branch loop relative to the normal direction of flow of the atmosphere in the loop. It holds back contaminating elements when the atmosphere of the enclosure is circulated.
An enclosure of the above kind works well if the fan or the pump is not stopped and the atmosphere circulates through the branch loop.
Contamination of the branch loop is possible if the operation of the pump is interrupted. It is then necessary to decontaminate the whole of the branch loop before restarting the enclosure, which necessitates a great deal of work.
Also, if work on the branch loop necessitates stopping the pump, it is necessary to decontaminate both the confinement space and the branch loop before returning the enclosure to service.
An object of the invention is to propose a working enclosure which limits the need for manual decontamination of the confinement space and the branch loop.
To this end, the invention provides a working enclosure of the above type characterized in that it includes filter members at each end of said branch loop.
Particular embodiments of the enclosure have one or more of the following features:
the filtration members at each end of the branch loop extend the wall of the chamber through which the branch loop opens;
the working chamber includes a containment vessel and a door mobile relative to the containment vessel and shutting off an access to said containment space and the branch loop is carried by the door, each end of the branch loop opens via the door, and the filter members are carried by the door at each end of the branch loop;
the door has over most of its surface a thermostatically controlled box-section and said branch loop extends over most of its length inside said thermostatically controlled box-section;
the working chamber includes a containment vessel and a door mobile relative to the containment vessel and shutting off an access to said confinement space and each end of the branch loop opens through walls of the containment vessel;
the containment vessel is at least partly surrounded by a thermostatically controlled jacket and said branch loop extends over most of its length inside said thermostatically controlled jacket; and
the containment vessel is at least partly surrounded by a thermostatically controlled jacket filled with a heat-conducting liquid and said branch loop passes through said jacket and extends over the greater part of its length in a thermostatically controlled box-section adjacent said jacket, which box-section contains a gas.